Fill valves are typically installed in the bottom of toilet tanks. The installation of the fill valves usually occurs in the field, but sometimes the fill valves are installed to the toilet tank in the factory. Typical fill valves include a one piece construction that is positioned in the tank with a bottom portion extending through a hole in a bottom wall of the tank. A nut is threaded to the bottom portion to secure against the bottom surface of the toilet tank.
Fill valves routinely fail due to constant use, hard water, and failed internal seals. Fill valves are typically replaced every 3 to 5 years. When they are replaced, an installer must use a bucket and towel, as the excess water that cannot be flushed (that pools beneath the edge of the flush valve) empties out the bottom of the tank. Moreover, the nut that secures the fill valve to the tank is below the tank, which may difficult to access. Finally, the entire fill valve is typically discarded during the replacement process.
Also, many fill valves are cracked or split during the installation when the installers are tightening the nut that connects the fill valve to the toilet tank or when the hose connector of a water supply is connected to the fill valve. When the fill valve is cracked or split, the whole fill valve must be replaced.
Finally, some fill valves have an over molded brass shank at the base. About 20% to 30% by volume of all fill valves sold in the United States have this over molded design. Unfortunately, when these fill valves fail, the brass shank is discarded with the fill valve.